The present invention relates to data storage systems, and more particularly, this invention relates to reducing compression-based aging effects, or “creep,” of a magnetic recording tape in a dual-reel cartridge.
In magnetic storage systems, magnetic transducers read data from and write data onto magnetic recording media. Data is written on the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media.
An important and continuing goal in the data storage industry is that of increasing the density of data stored on a medium. For tape storage systems, that goal has led to increasing the track and linear bit density on recording tape, and decreasing the thickness of the magnetic tape medium. However, the development of small footprint, higher performance tape drive systems has created various problems in the design of a tape head assembly for use in such systems.
In a tape drive system, the drive moves the magnetic tape over the surface of the tape head at high speed. Usually the tape head is designed to minimize the spacing between the head and the tape. The spacing between the magnetic head and the magnetic tape is crucial and so goals in these systems are to have the recording gaps of the transducers, which are the source of the magnetic recording flux in near contact with the tape to effect writing sharp transitions, and to have the read elements in near contact with the tape to provide effective coupling of the magnetic field from the tape to the read elements.
During non-operation, magnetic recording tapes are sometimes unloaded from tape drives, and stored for long durations of time. Changes in media lateral dimensions may occur during long periods of storage, such as long-term media creep (where the width of the tape creeps from its initial form, also known in the art as “aging”), which tends to occur over time when a tape is wound around a hub of a tape cartridge. Long-term media creep is particularly problematic when dealing with tape dimensional stability issues, as the two ends of the tape exhibit creep in different ways. The inner wraps of tape positioned closest to the cartridge hub tend to expand laterally over time due to the compressive stresses exerted thereon by the wraps of tape wound around them. Wraps positioned toward the outer diameter of the spool of tape are under less compressive stress, but are under higher tensile stresses, which tends to cause lateral contraction of the tape, i.e., the tape becomes narrower over time. Accordingly, the ends of the tape exhibit oppositely-oriented lateral dimensional changes.
When the dimensions of the tape, the head, or both change, various issues arise. During writing, the likelihood of overwriting shingled tracks increases. Overwritten data is often unrecoverable. Likewise, during readback, if readers are no longer over the tracks to be read, reading errors increase.